diff options
Diffstat (limited to 'block/vhdx.h')
| -rw-r--r-- | block/vhdx.h | 325 |
1 files changed, 325 insertions, 0 deletions
diff --git a/block/vhdx.h b/block/vhdx.h new file mode 100644 index 000000000..fb687ed2d --- /dev/null +++ b/block/vhdx.h @@ -0,0 +1,325 @@ +/* + * Block driver for Hyper-V VHDX Images + * + * Copyright (c) 2013 Red Hat, Inc., + * + * Authors: + * Jeff Cody <jcody@redhat.com> + * + * This is based on the "VHDX Format Specification v0.95", published 4/12/2012 + * by Microsoft: + * https://www.microsoft.com/en-us/download/details.aspx?id=29681 + * + * This work is licensed under the terms of the GNU LGPL, version 2 or later. + * See the COPYING.LIB file in the top-level directory. + * + */ + +#ifndef BLOCK_VHDX_H +#define BLOCK_VHDX_H + +/* Structures and fields present in the VHDX file */ + +/* The header section has the following blocks, + * each block is 64KB: + * + * _____________________________________________________________________________ + * | File Id. | Header 1 | Header 2 | Region Table | Reserved (768KB) | + * |----------|---------------|------------|--------------|--------------------| + * | | | | | | + * 0.........64KB...........128KB........192KB..........256KB................1MB + */ + +#define VHDX_HEADER_BLOCK_SIZE (64*1024) + +#define VHDX_FILE_ID_OFFSET 0 +#define VHDX_HEADER1_OFFSET (VHDX_HEADER_BLOCK_SIZE*1) +#define VHDX_HEADER2_OFFSET (VHDX_HEADER_BLOCK_SIZE*2) +#define VHDX_REGION_TABLE_OFFSET (VHDX_HEADER_BLOCK_SIZE*3) + + +/* + * A note on the use of MS-GUID fields. For more details on the GUID, + * please see: https://en.wikipedia.org/wiki/Globally_unique_identifier. + * + * The VHDX specification only states that these are MS GUIDs, and which + * bytes are data1-data4. It makes no mention of what algorithm should be used + * to generate the GUID, nor what standard. However, looking at the specified + * known GUID fields, it appears the GUIDs are: + * Standard/DCE GUID type (noted by 10b in the MSB of byte 0 of .data4) + * Random algorithm (noted by 0x4XXX for .data3) + */ + +/* ---- HEADER SECTION STRUCTURES ---- */ + +/* These structures are ones that are defined in the VHDX specification + * document */ + +typedef struct VHDXFileIdentifier { + uint64_t signature; /* "vhdxfile" in ASCII */ + uint16_t creator[256]; /* optional; utf-16 string to identify + the vhdx file creator. Diagnotistic + only */ +} VHDXFileIdentifier; + + +/* the guid is a 16 byte unique ID - the definition for this used by + * Microsoft is not just 16 bytes though - it is a structure that is defined, + * so we need to follow it here so that endianness does not trip us up */ + +typedef struct MSGUID { + uint32_t data1; + uint16_t data2; + uint16_t data3; + uint8_t data4[8]; +} MSGUID; + +#define guid_eq(a, b) \ + (memcmp(&(a), &(b), sizeof(MSGUID)) == 0) + +#define VHDX_HEADER_SIZE (4*1024) /* although the vhdx_header struct in disk + is only 582 bytes, for purposes of crc + the header is the first 4KB of the 64KB + block */ + +/* The full header is 4KB, although the actual header data is much smaller. + * But for the checksum calculation, it is over the entire 4KB structure, + * not just the defined portion of it */ +typedef struct QEMU_PACKED VHDXHeader { + uint32_t signature; /* "head" in ASCII */ + uint32_t checksum; /* CRC-32C hash of the whole header */ + uint64_t sequence_number; /* Seq number of this header. Each + VHDX file has 2 of these headers, + and only the header with the highest + sequence number is valid */ + MSGUID file_write_guid; /* 128 bit unique identifier. Must be + updated to new, unique value before + the first modification is made to + file */ + MSGUID data_write_guid; /* 128 bit unique identifier. Must be + updated to new, unique value before + the first modification is made to + visible data. Visbile data is + defined as: + - system & user metadata + - raw block data + - disk size + - any change that will + cause the virtual disk + sector read to differ + + This does not need to change if + blocks are re-arranged */ + MSGUID log_guid; /* 128 bit unique identifier. If zero, + there is no valid log. If non-zero, + log entries with this guid are + valid. */ + uint16_t log_version; /* version of the log format. Mustn't be + zero, unless log_guid is also zero */ + uint16_t version; /* version of th evhdx file. Currently, + only supported version is "1" */ + uint32_t log_length; /* length of the log. Must be multiple + of 1MB */ + uint64_t log_offset; /* byte offset in the file of the log. + Must also be a multiple of 1MB */ +} VHDXHeader; + +/* Header for the region table block */ +typedef struct QEMU_PACKED VHDXRegionTableHeader { + uint32_t signature; /* "regi" in ASCII */ + uint32_t checksum; /* CRC-32C hash of the 64KB table */ + uint32_t entry_count; /* number of valid entries */ + uint32_t reserved; +} VHDXRegionTableHeader; + +/* Individual region table entry. There may be a maximum of 2047 of these + * + * There are two known region table properties. Both are required. + * BAT (block allocation table): 2DC27766F62342009D64115E9BFD4A08 + * Metadata: 8B7CA20647904B9AB8FE575F050F886E + */ +#define VHDX_REGION_ENTRY_REQUIRED 0x01 /* if set, parser must understand + this entry in order to open + file */ +typedef struct QEMU_PACKED VHDXRegionTableEntry { + MSGUID guid; /* 128-bit unique identifier */ + uint64_t file_offset; /* offset of the object in the file. + Must be multiple of 1MB */ + uint32_t length; /* length, in bytes, of the object */ + uint32_t data_bits; +} VHDXRegionTableEntry; + + +/* ---- LOG ENTRY STRUCTURES ---- */ +#define VHDX_LOG_HDR_SIZE 64 +typedef struct QEMU_PACKED VHDXLogEntryHeader { + uint32_t signature; /* "loge" in ASCII */ + uint32_t checksum; /* CRC-32C hash of the 64KB table */ + uint32_t entry_length; /* length in bytes, multiple of 1MB */ + uint32_t tail; /* byte offset of first log entry of a + seq, where this entry is the last + entry */ + uint64_t sequence_number; /* incremented with each log entry. + May not be zero. */ + uint32_t descriptor_count; /* number of descriptors in this log + entry, must be >= 0 */ + uint32_t reserved; + MSGUID log_guid; /* value of the log_guid from + vhdx_header. If not found in + vhdx_header, it is invalid */ + uint64_t flushed_file_offset; /* see spec for full details - this + should be vhdx file size in bytes */ + uint64_t last_file_offset; /* size in bytes that all allocated + file structures fit into */ +} VHDXLogEntryHeader; + +#define VHDX_LOG_DESC_SIZE 32 + +typedef struct QEMU_PACKED VHDXLogDescriptor { + uint32_t signature; /* "zero" or "desc" in ASCII */ + union { + uint32_t reserved; /* zero desc */ + uint32_t trailing_bytes; /* data desc: bytes 4092-4096 of the + data sector */ + }; + union { + uint64_t zero_length; /* zero desc: length of the section to + zero */ + uint64_t leading_bytes; /* data desc: bytes 0-7 of the data + sector */ + }; + uint64_t file_offset; /* file offset to write zeros - multiple + of 4kB */ + uint64_t sequence_number; /* must match same field in + vhdx_log_entry_header */ +} VHDXLogDescriptor; + +typedef struct QEMU_PACKED VHDXLogDataSector { + uint32_t data_signature; /* "data" in ASCII */ + uint32_t sequence_high; /* 4 MSB of 8 byte sequence_number */ + uint8_t data[4084]; /* raw data, bytes 8-4091 (inclusive). + see the data descriptor field for the + other mising bytes */ + uint32_t sequence_low; /* 4 LSB of 8 byte sequence_number */ +} VHDXLogDataSector; + + + +/* block states - different state values depending on whether it is a + * payload block, or a sector block. */ + +#define PAYLOAD_BLOCK_NOT_PRESENT 0 +#define PAYLOAD_BLOCK_UNDEFINED 1 +#define PAYLOAD_BLOCK_ZERO 2 +#define PAYLOAD_BLOCK_UNMAPPED 5 +#define PAYLOAD_BLOCK_FULL_PRESENT 6 +#define PAYLOAD_BLOCK_PARTIALLY_PRESENT 7 + +#define SB_BLOCK_NOT_PRESENT 0 +#define SB_BLOCK_PRESENT 6 + +/* per the spec */ +#define VHDX_MAX_SECTORS_PER_BLOCK (1<<23) + +/* upper 44 bits are the file offset in 1MB units lower 3 bits are the state + other bits are reserved */ +#define VHDX_BAT_STATE_BIT_MASK 0x07 +#define VHDX_BAT_FILE_OFF_BITS (64-44) +typedef uint64_t VHDXBatEntry; + +/* ---- METADATA REGION STRUCTURES ---- */ + +#define VHDX_METADATA_ENTRY_SIZE 32 +#define VHDX_METADATA_MAX_ENTRIES 2047 /* not including the header */ +#define VHDX_METADATA_TABLE_MAX_SIZE \ + (VHDX_METADATA_ENTRY_SIZE * (VHDX_METADATA_MAX_ENTRIES+1)) +typedef struct QEMU_PACKED VHDXMetadataTableHeader { + uint64_t signature; /* "metadata" in ASCII */ + uint16_t reserved; + uint16_t entry_count; /* number table entries. <= 2047 */ + uint32_t reserved2[5]; +} VHDXMetadataTableHeader; + +#define VHDX_META_FLAGS_IS_USER 0x01 /* max 1024 entries */ +#define VHDX_META_FLAGS_IS_VIRTUAL_DISK 0x02 /* virtual disk metadata if set, + otherwise file metdata */ +#define VHDX_META_FLAGS_IS_REQUIRED 0x04 /* parse must understand this + entry to open the file */ +typedef struct QEMU_PACKED VHDXMetadataTableEntry { + MSGUID item_id; /* 128-bit identifier for metadata */ + uint32_t offset; /* byte offset of the metadata. At + least 64kB. Relative to start of + metadata region */ + /* note: if length = 0, so is offset */ + uint32_t length; /* length of metadata. <= 1MB. */ + uint32_t data_bits; /* least-significant 3 bits are flags, the + rest are reserved (see above) */ + uint32_t reserved2; +} VHDXMetadataTableEntry; + +#define VHDX_PARAMS_LEAVE_BLOCKS_ALLOCED 0x01 /* Do not change any blocks to + be BLOCK_NOT_PRESENT. + If set indicates a fixed + size VHDX file */ +#define VHDX_PARAMS_HAS_PARENT 0x02 /* has parent / backing file */ +typedef struct QEMU_PACKED VHDXFileParameters { + uint32_t block_size; /* size of each payload block, always + power of 2, <= 256MB and >= 1MB. */ + uint32_t data_bits; /* least-significant 2 bits are flags, the rest + are reserved (see above) */ +} VHDXFileParameters; + +typedef struct QEMU_PACKED VHDXVirtualDiskSize { + uint64_t virtual_disk_size; /* Size of the virtual disk, in bytes. + Must be multiple of the sector size, + max of 64TB */ +} VHDXVirtualDiskSize; + +typedef struct QEMU_PACKED VHDXPage83Data { + MSGUID page_83_data[16]; /* unique id for scsi devices that + support page 0x83 */ +} VHDXPage83Data; + +typedef struct QEMU_PACKED VHDXVirtualDiskLogicalSectorSize { + uint32_t logical_sector_size; /* virtual disk sector size (in bytes). + Can only be 512 or 4096 bytes */ +} VHDXVirtualDiskLogicalSectorSize; + +typedef struct QEMU_PACKED VHDXVirtualDiskPhysicalSectorSize { + uint32_t physical_sector_size; /* physical sector size (in bytes). + Can only be 512 or 4096 bytes */ +} VHDXVirtualDiskPhysicalSectorSize; + +typedef struct QEMU_PACKED VHDXParentLocatorHeader { + MSGUID locator_type[16]; /* type of the parent virtual disk. */ + uint16_t reserved; + uint16_t key_value_count; /* number of key/value pairs for this + locator */ +} VHDXParentLocatorHeader; + +/* key and value strings are UNICODE strings, UTF-16 LE encoding, no NULs */ +typedef struct QEMU_PACKED VHDXParentLocatorEntry { + uint32_t key_offset; /* offset in metadata for key, > 0 */ + uint32_t value_offset; /* offset in metadata for value, >0 */ + uint16_t key_length; /* length of entry key, > 0 */ + uint16_t value_length; /* length of entry value, > 0 */ +} VHDXParentLocatorEntry; + + +/* ----- END VHDX SPECIFICATION STRUCTURES ---- */ + + +uint32_t vhdx_checksum_calc(uint32_t crc, uint8_t *buf, size_t size, + int crc_offset); + +bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int crc_offset); + + +static void leguid_to_cpus(MSGUID *guid) +{ + le32_to_cpus(&guid->data1); + le16_to_cpus(&guid->data2); + le16_to_cpus(&guid->data3); +} + +#endif |